Structure of memory device having floating gate with protruding structure

ABSTRACT

A structure of memory device includes trench isolation lines in a substrate, extending along a first direction. An active region in the substrate is between adjacent two of the trench isolation lines. A dielectric layer is disposed on the active region of the substrate. A floating gate corresponding to a memory cell is disposed on the dielectric layer between adjacent two of the trench isolation lines. The floating gate has a first protruding structure at a sidewall extending along the first direction. A first insulating layer crosses over the floating gate and the trench isolation lines. A control gate line is disposed on the first insulating layer over the floating gate, extending along a second direction intersecting with the first direction. The control gate line has a second protruding structure correspondingly stacked over the first protruding structure of the floating gate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Chinese patentapplication serial no. 201910510488.5, filed on Jun. 13, 2019. Theentirety of the above-mentioned patent application is herebyincorporated by reference herein and made a part of this specification.

BACKGROUND 1. Field of the Invention

The present invention generally relates to semiconductor fabrication,and particularly to a structure of a memory device and method forfabricating method thereof.

2. Description of Related Art

The non-volatile memory device is almost an absolutely requiredequipment in a digital electronic product. The digital electronicproducts such as computer system, mobile phone, camera, video apparatus,and so on, are also the necessary products in the daily life. Therefore,the non-volatile memory device is commonly required.

The non-volatile memory device in an example is a flash memory,including a control gate and a floating gate. Since the data stored inthe flash memory are often changed according to the actual operation,the erasing operation of data is also often operated in addition to thereading operation and writing operation. In the storage operation for alarge amount of data, the efficiency for erasing data would influencethe whole performance of the memory device.

The cell structure of flash memory is still under development, so toexpect the improvement of the whole performance of the memory device, inwhich the efficiency for erasing data would necessarily be consideredand improved.

SUMMARY OF THE INVENTION

The invention provides a structure of memory device. For the structureof the memory device, both of the floating gate and the control gateline include a protruding part, so to produce more of the sharp cornerand sharp edge, which is advantageous to quickly remove the electronsout from the floating gate. As a result, the erasing efficiency may beimproved.

In an embodiment, the invention provides a structure of memory device.The structure of memory device includes a plurality of trench isolationlines in a substrate, extending along a first direction. An activeregion is in the substrate between adjacent two of the trench isolationlines. A dielectric layer is disposed on the active region of thesubstrate. A floating gate is disposed on the dielectric layercorresponding to a memory cell between adjacent two of the trenchisolation lines. The floating gate comprises a first protrudingstructure extending along the first direction from a sidewall of thefloating gate. A first insulating layer is crossing over the floatinggate and the trench isolation lines. A control gate line is disposed onthe first insulating layer over the floating gate, extending along asecond direction intersecting with the first direction. The control gateline has a second protruding structure correspondingly stacked over thefirst protruding structure of the floating gate.

In an embodiment, as to the structure of memory device, it furthercomprises an erase gate line between adjacent two of the control gateline, wherein the first protruding structure and the second protrudingstructure are extending toward the erase gate line.

In an embodiment, as to the structure of memory device, it furthercomprises a second insulating layer on a sidewall of the control gateline to insulate from the erase gate line.

In an embodiment, as to the structure of memory device, the firstinsulating layer and the second insulating layer comprises anoxide/nitride/oxide structure.

In an embodiment, as to the structure of memory device, a portion of thedielectric layer between the erase gate line and the substrate comprisesan oxide/nitride/oxide structure.

In an embodiment, as to the structure of memory device, the substratecomprises a doped line under the erase gate line to serve as a selectionline.

In an embodiment, as to the structure of memory device, the firstprotruding structure and the second protruding structure comprise asingle protruding bar, multiple protruding bars, single triangularprotruding part, multiple triangular protruding parts, zigzag-likeprotruding part, or wave-like protruding part.

In an embodiment, as to the structure of memory device, the secondprotruding structure is conformal to but smaller than the firstprotruding structure.

In an embodiment, as to the structure of memory device, a width of thesecond protruding structure of the control gate line is not greater thana width of the active region.

In an embodiment, as to the structure of memory device, the activeregion of the substrate comprises a doped region.

In an embodiment, as to the structure of memory device, it furthercomprises a word line extending along the second direction, abutting tothe floating gate and the control gate line at one side opposite to thefirst protruding structure and the second protruding structure.

In an embodiment, as to the structure of memory device, a top of thetrench isolation lines is higher than a bottom of the floating gate.

In an embodiment, as to the structure of memory device, a portion of thedielectric layer between the floating gate and the substrate furthercomprises a vertical portion between the trench isolation lines and alower part of the floating gate.

In an embodiment, as to the structure of memory device, the verticalportion of the dielectric layer comprises an oxide layer.

In an embodiment, as to the structure of memory device, the firstprotruding structure provides at least a sharp edge and a sharp cornerat an end part of the first protruding structure.

In an embodiment, the invention provides a structure of memory device.The structure of memory device comprises a plurality of trench isolationlines in a substrate, extending along a first direction. An activeregion is in the substrate between adjacent two of the trench isolationlines. A floating gate is disposed over the substrate between adjacenttwo of the trench isolation lines, wherein the floating gate has a firstprotruding structure extending out along the first direction from asidewall of the floating gate. A control gate line is disposed over thefloating gate, extending along a second direction intersecting with thefirst direction. The control gate line has a second protruding structurecorrespondingly stacked over the first protruding structure of thefloating gate. An insulating structure layer is to isolate the floatinggate from the control gate line.

In an embodiment, as to the structure of memory device, the firstprotruding structure and the second protruding structure comprise asingle protruding bar, multiple protruding bars, single triangularprotruding part, multiple triangular protruding parts, zigzag-likeprotruding part, or wave-like protruding part.

In an embodiment, as to the structure of memory device, the secondprotruding structure is conformal to but smaller than the firstprotruding structure.

In an embodiment, as to the structure of memory device, a width of thesecond protruding structure of the control gate line is not greater thana width of the active region.

In an embodiment, as to the structure of memory device, a top of thetrench isolation lines is higher than a bottom of the floating gate.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a drawing, schematically illustrating a layout of the memorydevice, according to an embodiment of the invention.

FIG. 2 is a drawing, schematically illustrating a cross-sectionalstructure of the memory device along a cutting line A-A′ in FIG. 1,according to an embodiment of the invention.

FIG. 3 is a drawing, schematically illustrating a cross-sectionalstructure of the memory device along a cutting line B-B′ in FIG. 1,according to an embodiment of the invention.

FIG. 4A to FIG. 4D are drawings, schematically illustrating thestructures of the control gate line of the memory device in top view,according to an embodiment of the invention.

FIG. 5 is a drawing, schematically illustrating a layout of the memorydevice, according to an embodiment of the invention.

FIG. 6 is a drawing, schematically illustrating a cross-sectionalstructure of the memory device along a cutting line A-A′ in FIG. 5,according to an embodiment of the invention.

FIG. 7 is a drawing, schematically illustrating a cross-sectionalstructure of the memory device along a cutting line B-B′ in FIG. 5,according to an embodiment of the invention.

FIG. 8 is a drawing, schematically illustrating a cross-sectionalstructure of the memory device along a cutting line C-C′ in FIG. 5,according to an embodiment of the invention.

FIG. 9 is a drawing, schematically illustrating a perspective structureof the control gate line with the floating gate of the memory device,according to an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

The invention is directed to a structure of memory device. According toan embodiment of the invention, in the structure of memory device asprovided in the invention, both of the floating gate and the controlgate line in the memory cell have protruding structures in similarshape, so to produce more of sharp corners and sharp edges. Thisstructure is advantageous to quickly remove the electrons out from thefloating gate during the erasing operation, at least the erasingefficiency may be improved.

Multiple embodiments are provided for describing the invention but theinvention is not just limited to the embodiments as provided. Inaddition, a proper combination between the embodiments may also be made.

The invention has looked into the structure of memory device, so tomodify the structure of memory device as intended, then the operationefficiency of the memory device may be improved.

FIG. 1 is a drawing, schematically illustrating a layout of the memorydevice, according to an embodiment of the invention. FIG. 2 is adrawing, schematically illustrating a cross-sectional structure of thememory device along a cutting line A-A′ in FIG. 1, according to anembodiment of the invention. FIG. 3 is a drawing, schematicallyillustrating a cross-sectional structure of the memory device along acutting line B-B′ in FIG. 1, according to an embodiment of theinvention.

Referring to FIG. 1 to FIG. 3 together, the structure of memory devicein an example is a flash memory. A number of memory cells of the memorydevice in an array manner are formed on the substrate 100. The substrate100 is configured into multiple trench isolation lines 60 in thesubstrate 100, extending along a first direction. The first direction inan example is the direction of the cutting line A-A′. Multiple activeregions 50 are in the substrate and between adjacent two trenchisolation lines 60. The active regions 50 may be in a form of activelines. The dielectric layer 102 is at least disposed on the activeregion 50. The active regions 50 of the substrate 100 may have a dopedregion 52.

As to the operation mechanism to the memory cell, the memory cellincludes a floating gate FG, disposed on the dielectric layer 102,located between adjacent two of the trench isolation lines 60. A portionof the dielectric layer 102 between the floating gate FG and thesubstrate 100 is serving as a gate insulating layer. The floating gateFG is implemented corresponding to each memory cell. In addition, thecontrol gate line CG of the memory cell is extending along the seconddirection, connecting a string of memory cells. The second direction inan example is the direction of the cutting line B-B′, intersecting withthe first direction, such as perpendicular intersection. The controlgate line CG is over the floating gate FG, and is isolated by theinsulating layer 104. The insulating layer 104 in an embodiment isoxide/nitride/oxide (ONO) structure. The erase gate line EG is on thesubstrate 100, located between the floating gates FG and also betweenadjacent two control gate lines CG. The isolation between the erase gateline EG and the substrate 100 is provided from a portion of thedielectric layer 102. The substrate 100 has the doped region 52 underthe erase gate line EG to server as the selection line SL as needed inactual operation. The outer side of the floating gate FG and the controlgate line has the word lines WL. A dielectric layer 106 is between theword line WL and the floating gate FG to isolate each other. Further, aninsulating layer 108 is also between the word line WL and the erase gateline EG. In an example, it may also be the ONO structure. A dielectriclayer 110 and a mask layer 112 may also be disposed on top of thecontrol gate line CG, so to further protect the control gate line CG.

Here, the insulation between the floating gate FG, the control gate lineCG, the erase gate line EG, word line WL, and the substrate 100 is doneby the dielectric material. Each portion of the dielectric material maybe formed according to the actual need. The invention is not necessaryto be limited to a specific structure.

In addition, as viewed from FIG. 3, the dielectric layer 206 is toisolate between the floating gate FG and the substrate 100 but a top ofthe trench isolation line 60 in an example is lower than a bottom of thefloating gate FG. The floating gate FG and the control gate line CG areisolated therebetween by the insulating layer 104.

In considering the foregoing structure of memory device, the charges asstored in the floating gate FG during the erasing operation would beremoved out by the erasing gate line EG. As having been observed in theinvention, a capacitor path is formed between the floating gate FG andthe erase gate line EG through the dielectric layer 106. As a result,the charges during the erasing operation are removed out from thefloating gate FG. It is similar in circuit effect that the charges aredriven out from a capacitor. Further, the invention has looked into indetail about the mechanism to remove the charges out. An electric fieldwith a strength as produced by the operation voltage is applied to thecharges, so to produce the driving force on the charges, in which a tipdischarge phenomenon may more easily cause the charges to leave out fromthe structure body.

After looking into the mechanism in the invention, the invention hasproposed a structure for the control gate line CG and the floating gateFG, so to improve the efficiency to remove the charges out from thefloating gate FG. FIG. 4A to FIG. 4D are drawings, schematicallyillustrating the structures of the control gate line of the memorydevice in top view, according to an embodiment of the invention.

Referring to FIG. 4A, taking a memory cell corresponding to a controlgate line 200 as an example, the protruding structure 300 may be added.The protruding structure 300 is protruding toward the erase gate lineEG. Here, the erase gate line EG is just schematically illustrating theimplementation relation between the control gate line CG and thefloating gate FG, which is under the control gate line CG. Thedielectric layer as actually needed between the control gate line CG andthe floating gate FG in FIG. 4A is omitted without descriptions indetail. The protruding structure 300 of the control gate line 200, in anexample, is a single protruding bar, which may additionally produce thenumber of the sharp corner 120 and the sharp edge 122 and then therebyimprove the efficiency to remove the charges from the floating gate FG,which is under the control gate line CG.

With the aspect of the protruding structure 300, the geometric shape mayhave various options. Referring to FIG. 4B, the protruding structure 300may be a single triangular protruding part, which may also additionallyprovide the sharp corner 120 and the sharp edge 122.

Further referring to FIG. 4C, according to the protruding structure 300in FIG. 4B, the protruding structure 300 may be multiple triangularprotruding parts, which may even further be realized as zigzag-likeprotruding part or wave-like protruding part. Referring to FIG. 4D,according to the protruding structure 300 in FIG. 4A, the protrudingstructure 300 may be multiple protruding bars.

The protruding structure 300 in actual design may also be a combinationfrom the manners in FIG. 4A to FIG. 4D, so to have the protrudingstructure 300 as intended, so to provide more of the sharp corner 120and the sharp edge 122.

FIG. 5 is a drawing, schematically illustrating a layout of the memorydevice, according to an embodiment of the invention. Referring to FIG.5, the control gate line CG of the invention corresponding to the memorycell in design has been added with the protruding structure 300, inwhich the control gate line CG includes the protruding structure 300 incomparison to the layout in FIG. 1. The protruding structure 300 extendsout from the sidewall to the erase gate line EG, along the direction ofthe cutting line A-A′.

As viewed from the cross-sectional structure, FIG. 6 is a drawing,schematically illustrating a cross-sectional structure of the memorydevice along a cutting line A-A′ in FIG. 5, according to an embodimentof the invention. FIG. 7 is a drawing, schematically illustrating across-sectional structure of the memory device along a cutting line B-B′in FIG. 5, according to an embodiment of the invention. FIG. 8 is adrawing, schematically illustrating a cross-sectional structure of thememory device along a cutting line C-C′ in FIG. 5, according to anembodiment of the invention.

Referring to FIG. 6, the cross-section structure at the cutting lineA-A′ is similar to the structure in FIG. 2. The substrate 100 at leasthas dielectric layer 220 thereon on active region 50, to have theinsulation between various gate lines and the substrate 100. The memorycell includes the floating gate FG 208, dispose don the dielectric layer220. The active region 50 is disposed between adjacent two trench lines600. A dielectric portion 220 b of the dielectric layer 220 between thefloating gate FG 208 and the substrate 100 serves as the gate insulatinglayer. The floating gate FG 208 is implemented corresponding to eachmemory cell. In addition, the control gate line CG of the memory cell isextending along the second direction to connect a string of memorycells. The second direction in an example is the direction of thecutting line B-B′, intersecting with the first direction, such asperpendicular intersection. The control gate line CG 200 is above thefloating gate FG 208, and isolated by the insulating layer 222. Theinsulating layer 222 in an example is the ONO structure. The erase gateline EG 202 is over the substrate 100, disposed between the floatinggates 208 and also between adjacent two control gate lines 200.

The erase gate line EG 202 in the embodiment is shared by two memorycells, as an example, so that it is between adjacent two control gatelines CG 200. A dielectric portion 220 a of the dielectric layer 220 isfor isolation between the erase gate line EG 202 and the substrate 100.The dielectric portion 220 a in an example is a single oxide layer orthe ONO structure without being specifically limited.

Here, the doped region in the substrate 100 has been omitted withoutfurther descriptions. The outer side of the floating gate FG 208 and thecontrol gat e line 200 has the word line WL 206. The dielectric layer220 is also disposed between the word line WL 206 and the floating gateFG 208 to isolate to each other. In addition, the dielectric layer 224is also disposed between the word line WL 206 and the control gate lineCG 200 to isolate to each other. The insulating layer 224 in verticaldirection is on the sidewall of the control gate line CG 200 and may bethe ONO structure in an example. The top of the control gate line CG 200may also have the dielectric layer 226 and the mask layer 210 to furtherprotect the control gate line CG 200.

The insulation between the floating gate FG 208, the control gate lineCG 200, the erase gate line EG 202, the word line WL 206 and thesubstrate 100 may be accomplished by dielectric material. The structureof individual portion of the dielectric material may be formed accordingto actual design. The invention is not limited to a specific structure.

Referring to FIG. 7, the floating gate FG 206 is isolated from thesubstrate therebetween by the dielectric portion 220 b but the top ofthe trench isolation line 600 is higher than the bottom of the floatinggate FG 208. The floating gate FG 208 and the control gate line CG 200is isolated by the insulating layer 222 therebetween.

Referring to FIG. 8, it is cross-sectional structure on the cutting lineC-C′, in which the protruding structure 300 as proposed in the inventionwith respect to the control gate line CG 200 may be observed. Thefloating gate FG 208 under the control gate line CG 200, based on thefabrication flow, has the protruding structure 208 a, which would befurther described in FIG. 9.

The size of the protruding structure 300 for example is less than awidth of the active region. In an embodiment, the erase gate line EG 202is shared by two memory cells. As such, the protruding structures 300 oftwo control gate line CG 200 are facing to each other but separate by aproper distance without contacting to each other.

FIG. 9 is a drawing, schematically illustrating a perspective structureof the control gate line with the floating gate of the memory device,according to an embodiment of the invention. Referring to FIG. 9, as tothe arrangement in fabrication flow, when the control gate line CG 200with the protruding structure is formed, the floating gate FG 208 underthe control gate line CG 200 may be also etched, so that the protrudingstructure 208 a of the floating gate FG 208 may also be formed. Theprotruding structure 208 a of the floating gate FG 208 and theprotruding structure 300 of the control gate line CG 200 are similar inshape. In an embodiment, the size of the protruding structure 300 withrespect to the protruding structure 208 a may be shrink by a little butthe invention is not limited to this manner.

The floating gate FG 208 of the invention may obtain the protrudingstructure 208 a in accordance with the protruding structure 300 of thecontrol gate line CG 200. Except the original sharp corner 304 and thesharp edge 302 of the floating gate FG 208, the protruding structure 208a further provides the sharp corner 306 and the sharp edge 208 b, so toimprove the discharging effect.

As to the foregoing the descriptions of multiple embodiments, in thestructure of the memory device provided by the invention, the floatinggate and the control gate line of the memory cell have the similarprotruding structures extending toward the erase gate line. Theprotruding structure of the floating gate, associating with the controlof the control gate line, provides more of sharp corners and sharpedges. This, the structure is advantageous to quickly remove the chargesas stored in the floating gate during the erasing operation. The erasingefficiency may at least be improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A structure of memory device, comprising: a plurality of trenchisolation lines in a substrate, extending along a first direction; anactive region in the substrate between adjacent two of the trenchisolation lines; a dielectric layer on the active region of thesubstrate; a floating gate, disposed on the dielectric layercorresponding to a memory cell between adjacent two of the trenchisolation lines, wherein the floating gate comprises a first protrudingstructure extending along the first direction from a sidewall of thefloating gate; a first insulating layer crossing over the floating gateand the trench isolation lines; and a control gate line, disposed on thefirst insulating layer over the floating gate, extending along a seconddirection intersecting with the first direction, wherein the controlgate line has a second protruding structure correspondingly stacked overthe first protruding structure of the floating gate.
 2. The structure ofmemory device of claim 1, further comprising an erase gate line betweenadjacent two of the control gate line, wherein the first protrudingstructure and the second protruding structure are extending toward theerase gate line.
 3. The structure of memory device of claim 2, furthercomprising a second insulating layer on a sidewall of the control gateline to insulate from the erase gate line.
 4. The structure of memorydevice of claim 3, wherein the first insulating layer and the secondinsulating layer comprises an oxide/nitride/oxide structure.
 5. Thestructure of memory device of claim 2, wherein a portion of thedielectric layer between the erase gate line and the substrate comprisesan oxide/nitride/oxide structure.
 6. The structure of memory device ofclaim 2, wherein the substrate comprises a doped line under the erasegate line to serve as a selection line.
 7. The structure of memorydevice of claim 1, wherein the first protruding structure and the secondprotruding structure comprise a single protruding bar, multipleprotruding bars, single triangular protruding part, multiple triangularprotruding parts, zigzag-like protruding part, or wave-like protrudingpart.
 8. The structure of memory device of claim 1, wherein the secondprotruding structure is conformal to but smaller than the firstprotruding structure.
 9. The structure of memory device of claim 1,wherein a width of the second protruding structure of the control gateline is not greater than a width of the active region.
 10. The structureof memory device of claim 1, wherein the active region of the substratecomprises a doped region.
 11. The structure of memory device of claim 1,further comprising a word line extending along the second direction,abutting to the floating gate and the control gate line at one sideopposite to the first protruding structure and the second protrudingstructure.
 12. The structure of memory device of claim 1, wherein a topof the trench isolation lines is higher than a bottom of the floatinggate.
 13. The structure of memory device of claim 12, wherein a portionof the dielectric layer between the floating gate and the substratefurther comprises a vertical portion between the trench isolation linesand a lower part of the floating gate.
 14. The structure of memorydevice of claim 13, wherein the vertical portion of the dielectric layercomprises an oxide layer.
 15. The structure of memory device of claim 1,wherein the first protruding structure provides at least a sharp edgeand a sharp corner at an end part of the first protruding structure. 16.A structure of memory device, comprising: a plurality of trenchisolation lines in a substrate, extending along a first direction; anactive region in the substrate, between adjacent two of the trenchisolation lines; a floating gate, disposed over the substrate betweenadjacent two of the trench isolation lines, wherein the floating gatehas a first protruding structure extending out along the first directionfrom a sidewall of the floating gate; a control gate line, disposed overthe floating gate, extending along a second direction intersecting withthe first direction, wherein the control gate line has a secondprotruding structure correspondingly stacked over the first protrudingstructure of the floating gate; and an insulating structure layer, toisolate the floating gate from the control gate line.
 17. The structureof memory device of claim 16, wherein the first protruding structure andthe second protruding structure comprise a single protruding bar,multiple protruding bars, single triangular protruding part, multipletriangular protruding parts, zigzag-like protruding part, or wave-likeprotruding part.
 18. The structure of memory device of claim 16, whereinthe second protruding structure is conformal to but smaller than thefirst protruding structure.
 19. The structure of memory device of claim16, wherein a width of the second protruding structure of the controlgate line is not greater than a width of the active region.
 20. Thestructure of memory device of claim 16, wherein a top of the trenchisolation lines is higher than a bottom of the floating gate.